Does the demonstrated diagram look familiar to you? A lot of applications will look just like so.
Without any IoC or Dependency Injection framework / libraries, those applications will suffer from those issues
- Everything centralized in
main
method, and will be scattered to all services - The higher level of the component you want to test, it'll be more complicated to setup tests
Tak Register user handler
as an example, to setup the test for it
- You'll need to mock
User service
- Or you'll need to mock
Db connection
- Or you'll need to mock
Config
Submodule
was born to balance the Ioc wiring, so you don't have to pull your hairs just to test your app
Submodule is built around the concept of function composition. A component will be hidden/lazy initialized behind a function. And if another module requires that component, submodule will associate those factory functions. The initialization will only happen when one of those components got used
So, Submodule will just replicate exactly what described as dependencies in the diagram, and only initialized when one of those components got called
Then, with the knowledge of dependencies like so, Submodule will initialize just what it is needed to support testing
package main
import (
"fmt"
"net/http"
"github.com/submodule-org/submodule.go/v2"
)
type Config struct {
Host string
Port int
LogLevel string
}
func LoadConfig() Config {
// load config from ENV etc
return Config{
Host: "", // value from env or default value
Port: 0, // value from env or default value
LogLevel: "debug", // value from env or default value
}
}
// ConfigMod will be the singleton container for config value
var ConfigMod = submodule.Make[Config](LoadConfig)
type logger struct {
LogLevel string
}
type Logger interface {
Log(msg ...string)
}
func (l *logger) Log(msgs ...string) {
// log implementation with log level
}
var LoggerMod = submodule.Make[Logger](func(config Config) Logger {
return &logger{
LogLevel: config.LogLevel,
}
}, ConfigMod)
type server struct {
Config Config
Logger Logger
}
func (s *server) Start() {
go func() {
http.ListenAndServe(fmt.Sprintf("%s:%d", s.Config.Host, s.Config.Port), nil)
}()
}
var ServerMod = submodule.Resolve(&server{}, ConfigMod, LoggerMod)
func main() {
server := ServerMod.Resolve()
server.Start()
}